Slate roof for an outhouse?

If your replacing the complete roof its up to your self what covering you use as any new trusses would have to comply with current building regs which would mean they would be able to take the weight of heavier concrete tiles if necessary. Manufactures Say concrete 70+ life span Clay 60+life span Slate 35+ life span unless it welsh slate then it100+yrs life span In reality clay or slate will last the longest Concrete will be the easiest & cheapest to lay. Just noticed you say you have felt at the moment so there may not be enough of a pitch to be able to treat it as anything other than a flat roof. In which case I would recommend E.P.D.M. rubber roof it will out last anything else on the market at the moment Hope this helps you a bit. 2-3 days if your replacing everything Good luck Alex .

Slate would be an excellent option, spanish slates are reasonably cheap and look great. watch some youtube videos on slating if you are a DIYer. When building the structure remember to allow for adequate pitch, its supposed to be about 20 degree but you can go less (around 15 degree) on a single storey building thats partly sheltered by the house. For a roofer and a labourer to strip, build roof structure felt, batten and slate would be 1-2 days. For a DIYer it will take between 1 and 4 days depending on your capabilities.